The invention relates generally to controlling circulators used in hydronic heating and cooling systems.
Such systems are often divided into zones, each zone serving a separate portion of a building and each zone controlled by its own thermostat. This allows a different temperature to be maintained in each area being heated or cooled. Zoning, i.e., diverting operating fluid into a given zone when necessary, is generally achieved using zone valves or circulators.
When zoning with circulators, a thermostatically-controlled pump is used to deliver operating fluid into each separate zone. As is most often found in the art today, a separate controller--containing a transformer and a switching element (e.g., relay)--controls the circulator for each zone. The transformer steps line voltage (usually 115 volts) down, usually to 24 volts. A thermostat in the particular zone controls the relay, the coil of which operates at the stepped-down voltage. When the relay contacts close, line voltage is passed to the pump, thereby powering the circulator.
In some examples of the existing art, a controller consisting of one transformer and several relays--one relay for each zone--is utilized. A thermostat in each zone controls each relay, and each relay passes line voltage to the circulator in the given zone.
Various forms of circulators are known. Some circulators employ a separate electrical motor coupled to a separate pump. Another form of circulator is the so-called "wet-rotor" circulator, in which the pump and motor are integrated, resulting in a more compact overall circulator unit. In a wet-rotor circulator, the rotor is supported within a rotor housing into which the fluid being circulated is allowed to enter (the fluid helps to lubricate the rotor bearings). The rotor housing is supported within a surrounding stator, which is sealed from the circulating fluid.
In most hydronic systems, electric motors are used to drive most circulator pumps with the pump impeller being mounted on a motor shaft extension. Other circulators are flexibly coupled through a pump mounting bracket or frame to the electric motor.
A number of variable-speed drive devices are available for operating such circulators, including fluid coupling, SCR variable frequency, direct current, wound rotor, and eddy current drives.